In many, if not most, procedures involving a person's (patient's) temporo-mandibular joint, it is at least highly desirable, if not totally necessary, to be able to inspect such temporo-mandibular joint by means of an X-ray image. The temporo-mandibular joint (often referred to as the "TMJ") is the articulation of the mandible with the temporal bone component of the cranium.
Such an inspection of the TMJ as by the production of what might be referred to as a standard lateral cephalogram (one that is produced as by the X-ray axis being perpendicular to the mid-sagital plane and the X-ray film being parallel to the mid-sagital plane) is not satisfactory. More particularly, because the juxtaposed cooperating surfaces of the TMJ are not necessarily perpendicular to the mid-sagital plane of the patient's cranium, a standard lateral cephalogram, or the like, taken of such TMJ often produces shadow type or overlapping images, on the X-ray image, which obscures or at least leaves in doubt the true nature or condition of the TMJ being inspected or monitored. Another factor, which not only in itself was a problem but further compounded the problem hereinbefore stated, namely the production of misleading shadows and overlapping images, was that more often than not a patient being treated for any TMJ related problem must have a series of X-ray images taken at selected spaced intervals of time (such may be spaced, for example, in terms of weeks or months) so as to enable the practitioner to observe the effects of the corrective procedures performed on the patient and to determine whether healing is occurring as desired or if further corrective procedures are indicated.
Because such X-ray images are spaced in time, the problem heretofore was one of attempting to position the patient's head, at each succeeding X-ray exposure, as nearly as possible to that position which the patient's head assumed at the immediately preceding X-ray exposure so that in comparing succeeding X-ray images the practitioner could rely upon the observed differences in the compared X-ray images as being a true and accurate indication of the actual changes occurring, during healing, as at the TMJ. However, heretofore, it has not been possible to so orient or position the patient's head, at every succeeding (time-spaced) X-ray exposure as to be assured that the patient's head was actually in the same position (as during the immediately prior X-ray exposure) or at least so close to the same position that the remaining degree of variance would not result in producing misleading X-ray images.
The prior art, in an attempt to avoid taking lateral cephalograms for the continued inspection and monitoring of the TMJ, had started to take the radiographs by aiming the axis of, for example, the source of the X-ray radiation so that such axis passes generally through the patient's cranium and through the TMJ. This, the prior art has done by causing the said axis to be at selected angles posterior and superior to the patient's cranium. However, this has not proven to be successful in that the procedure is one often based on a guess of appropriate aiming of the X-ray axis and the resulting X-ray image may be effectively useless because of interference to the X-ray radiation more often than not caused by the upward extension of the petrous ridge of the petrous bone of the temporal bone. Such bone, and ridge, (one on each side of the mid-sagital plane) extends generally from the side transversely of the cranium and angulates from such side generally forwardly of the cranium. Especially with patients where the prior art had to significantly increase the angular degrees of posterior setting of the X-ray axis, the petrous bone (on the same side as the TMJ being X-rayed) would cause greater and greater interference to the X-ray and produce unwanted images on the resulting X-ray image often causing such X-ray image to be totally useless in determining the then condition of the TMJ. It should be mentioned that the term "posterior" or "posterior setting" means the angle with respect to generally the back of the cranium or with respect to the transporionic axis as viewed from the top of the patient's head. Still another way of defining the "posterior setting" would be to say that it is that angle which the axis of the X-ray appears to make with respect to a plane parallel to the patient's transporionic axis when the back of the patient's head is selectively properly positioned operatively against or with respect to such a plane.
The invention as herein disclosed and described is primarily directed to the solution of the aforementioned and other related and attendant problems of the prior art.